I've just release version 0.3.3 of rdf-n3 [1], rdf-rdfa [2] and rdf-rdfxml [3], piggybacking on Arto's recent update of RDF.rb [4] to work around problems related to the 2.2.5 update to addressable [5].
Significant in this release, is that all 3 gems are now free and unencumbered public-domain software, using the same UNLICENSE model as RDF.rb.
Along with minor bug fixes, the RDFa Gem now includes a complete writer using Haml templates. This means that developers can either use one of the three canned templates included with the gem, or create their own, allowing the generation of arbitrary HTML including the RDFa markup of the serialized triples. To check this out, you can try it out at http://rdf.kellogg-assoc.com/distiller. Select the "rdfa" output format for a table-based template that uses some basic styling. the "html", "xhtml", or "svg" use an alternate template.
Coming in 0.4 is full SPARQL 1.0 support using sparql-algebra [6] and sparql-grammar [7] gems which will ultimately allow a completely native implementation of SPARQL 1.0 in native Ruby. Right now, it works against RDF::Repository, but will work with rdf-do, and rdf-sesame and other repositories eventually. The 0.4.x branch of rdf-spec [8] include specs that can be run against RDF::Queryable implementations to ensure conformance with SPARQL::Algebra semantics.
Update:
rdf-rdfa version 0.3.3.1 now uses HTML rather than XML parsing for text/html documents, and XML for application/xhtml+xml or other documents.
Gregg
[1] https://rubygems.org/gems/rdf-n3
[2] https://rubygems.org/gems/rdf-rdfa
[3] https://rubygems.org/gems/rdf-rdfxml
[4] https://rubygems.org/gems/rdf
[5] https://rubygems.org/gems/addressable
[6] https://github.com/gkellogg/sparql-algebra
[7] https://github.com/gkellogg/sparql-grammar
[8] https://rubygems.org/gems/rdf-spec